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Re: Looking for cheap boost chip 1.5v for LED

the little dorcy 1AAA LED flashlight has one in it , not sure how far it can pull down the cells though. Might be cheaper to buy that light for $6 at the store than have something shipped, hard to say though.

Re: Looking for cheap boost chip 1.5v for LED

the dorcy 1AAA 2nd gen measures off my multimeter at 240ma
since its a DC-DC step up, the LED's not getting 240ma, thats for sure...from the output I'd say its around there

I built this guy from scratch...and I'm out of 150uF electrolytic caps, so I used two 100uF caps
using a new 1.5V alkaline AA It can boost to 3.3V, sufficient to light up a RX1H luxeon star...at about 100ma

Re: Looking for cheap boost chip 1.5v for LED

Originally Posted by ken2400

Saw that. Can I buy the coil from digi-Key? Which one.

Thanks

unfortunately the coil is the most difficult part of the joulethief, and it has to be homemade because the schematics require it to have 4 wires instead of the usual 2, meaning you'll need a ferrite coil and wound one yourself. none of my homemade inductors as per the joulethief instructions actually gave me a light

Re: Looking for cheap boost chip 1.5v for LED

Hey jtr, is the inductor in that design commercially available, or does it have to be hand-wound like the Joule Thief's? It looks a little more complex, but if it doesn't require any hand-made components, it could be pretty handy.

Re: Looking for cheap boost chip 1.5v for LED

Originally Posted by TigerhawkT3

Hey jtr, is the inductor in that design commercially available, or does it have to be hand-wound like the Joule Thief's? It looks a little more complex, but if it doesn't require any hand-made components, it could be pretty handy.

It's just a standard commercially available inductor. No hand winding required.

Re: Looking for cheap boost chip 1.5v for LED

Voltage of C1 doesn't really matter as it sees no more than perhaps 4 volts. Most ceramics are rated at 50V at least.

BTW, with some tweaking and changing of values it's possible to use this circuit to drive far more than one LED. I made a version which powers two strings of 14 LEDs in series from 4.8 volts (4 AA batteries in series). I don't remember what component values I used offhand as that was about 3 years ago. The circuit as shown drives the LED with an average of roughly 20 mA when powered by a AA cell. You can decrease R2 to increase the drive current, and vice versa.

All you need to change is the inductor value to get the appropriate current output.

I don't think it gets easier than this, my soldering suck so SOT23 is no good for me because its a SMT component. but so far I haven't been able to find one that has it in the easy TO-220 packages

minimum startup: 0.9V and could operate between 0.7V and 1.9V at 25C
if the circuit is completed with 10uH inductor + 1 LED Vcc = 1.5V
LED peak Vf [5.8V], mean current [20ma], mean supply current [70ma], efficiency [77%]

these values are from a datasheet I have on the hard drive...I haven't been able to locate the right link to post to this post